Fixed-bearing unicompartmental knee arthroplasty. Patients’ selection and operative technique

Abstract

Unicompartmental knee arthroplasty (UKA) is designed for patients presenting arthritic wear limited to a single medial or lateral tibiofemoral compartment. The indication is based on strict criteria. Wear must stem from degenerative osteoarthritis or be secondary to aseptic necrosis of the medial condyle. Inflammatory rheumatism is a contraindication. Age and activity level should be compatible with an indication for arthroplasty. The body mass index should be less than 30 kg/m(2). The ligament system must be intact, particularly both cruciate ligaments. Any pre-existing axis deformity should be moderate and the residual axis deformity, after correction of wear with a unicompartmental tibial augmentation spacer, should not exceed 7-10° varus or valgus. These highly restrictive conditions result in the ideal indications for UKA suitable for no more than 15-20% of knee arthroplasty candidates for most surgeons experienced in this procedure. Although the results of certain early series worried potential users, today it can be asserted that recent series whose indications and technique correspond to modern use criteria, have shown results that are as reliable as those of total knee arthroplasty (TKA) at a 10 years' follow-up. Beyond this time frame, the risk of polyethylene wear related to the technical restrictions of the UKA is another consideration. Indeed, to prevent the risk of rapid extension of osteoarthritis to the opposite compartment, the procedure should be limited to restoring the patient's constitutional axis before wear phenomena had set in. This makes UKA a surgical procedure at risk of failure due to wear phenomena. Much of this paper will describe the precise rules for UKA positioning, which are critical to observe to warrant these implants outcome and longevity.

Preoperative pain location is a poor predictor of outcome after Oxford unicompartmental knee arthroplasty at 1 and 5 years

“…Kozinn and Scott [18] Bert [5] suggested that the ideal patient for UKA should be able to pinpoint their pain to the medial joint line (the 'one finger sign') rather than feeling pain generally within the knee (the 'knee grab sign'). Whilst no evidence-base exists to support this practice, it has been adopted by other authors as a prerequisite for UKA [10,14,27].…”

Medial Unicompartmental Knee Arthroplasty: Correlation Between Components’ Malalignment and Long-term Outcome in Obese Patients

“…In case of excessive tibial cut, tibial component is placed to the more fragile cancellous zone, the contact point of the femoral pad shifts to the periphery of the tibial plateau that leads to tibial loosening (5,28,29). Minimal tibial resection leads to overcorrection, joint line elevation (30), and -according to our study -to degenerative changes in lateral tibiofemoral joint.…”

“…It should extend to the medial margin of the tibia or overhang by up to 2 mm (2, 3). There is no height difference between the line of tibial component joint surface and the lateral tibiofemoral joint space (LTF), the tibial component joint surface is parallel with the LTF joint space (4,5) and there is no change in tibial slope (TS) compared with the preoperative position in the sagittal plane (4,5). In frontal plane, the femoral component is perpendicular to the tibial component joint surface (4,5), the component is positioned centrally on the medial femoral condyle (6), in sagittal plane the anterior edge of femoral component is in the same level with the line of the remaining cartilage (7).…”

“…Several articles have been published about the range of acceptable components' malalignment (3)(4)(5)(6)(8)(9)(10)(11).…”

Does Intraarticular Inflammation Predict Biomechanical Cartilage Properties?

“…Successful outcomes with UKA require strict observation of indications [12]. One of the most important factors influencing long-term survival is the condition of cartilage in the opposite femorotibial compartment [48].…”